SciShow Rocks Box: Tourmaline

• Mineral Name: Cyclosilicate
• Locality: Himalaya Mine, California

Tourmaline is a kind of silicate crystal that comes in tons of colors, depending on what minerals get mixed in while the crystal forms. Some geologists call tourmaline a “kitchen sink” mineral because of how many elements they can contain, which makes writing out its chemical formula very complicated.

But tourmaline is known for more than just being the stone with an identity crisis. It’s one of just a few materials that are pyroelectric, meaning that when you heat or cool it, the crystal will act like a magnet. This happens because of the crystalline structure of tourmaline, which has some parts that are more positively or negatively charged. Adding heat changes the distribution of charges within the crystal, giving you a more strongly charged positive and negative end.